Fluorogypsum waste solidification material

ABSTRACT

A process, and the product produced thereby, for the preparation of a waste solidification material from hardened fluorogypsum as a by-product of the manufacture of hydrofluoric acid by reacting fluorospar with sulfuric acid, removing hydrogen fluoride from the reaction product, slurrying the by-product with water, placing the slurried by-product fluorogypsum in settlement ponds until the fluorogypsum hardens, the hardened fluorogypsum having a pH of greater than about 5 to about 13, including heating the hardened fluorogypsum to evaporate substantially all water physically mixed with the fluorogypsum and further heating the fluorogypsum to reduce the water chemically bound to calcium sulfate in the fluorogypsum to form about 0.5% to about 9% by weight.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending U.S. patentapplication Ser. No. 07/299,127 filed Jan. 23, 1990.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a material for the solidification ofwaste products. In particular, the present invention relates to amaterial containing calcium sulfate useful for the solidification ofliquid industrial waste and sludge.

2. Description of the Related Art

The calcium sulfate from which the material of the invention is made isa by-product produced from the reaction of fluorspar with sulfuric acidin the production of hydrofluoric acid. The hydrogen fluoride is removedafter the reaction, while the by-product, which is predominantly calciumsulfate, is slurried with water and pumped into disposal ponds. Excesswater eventually evaporates and/or hydrates with calcium sulfate in theslurry and the by-product hardens. The by-product contains mostlycalcium sulfate anhydrite and calcium sulfate having water chemicallycombined therewith, plus small quantities of fluorine containingcompounds and small concentrations of sulfuric acid. The by-product issometimes referred to herein as fluorogypsum. The pH of the fluorogypsumis typically from about 3 to about 5 at some hydrofluoric acid plants,and about 3 to about 13 at other hydrofluoric acid plants.

Disposal ponds for fluorogypsum occupy large areas of useful land andcommonly require monitoring and maintenance by the owner. The disposalponds are constantly increasing in size and quantity of fluorogypsumcontained as hydrofluoric acid production continues.

Many materials are known for treating liquid and semiliquid waste andsludge to solidify the waste and render the waste fit for disposaland/or containment. Exemplary of the methods and materials for treatingliquid and semi-liquid waste and/or sludge are the following U.S.Patent:

U.S. Pat. No. 4,623,469 discloses a method for treating liquid andsemi-liquid wastes to render them fit for ultimate disposal, by firstdetermining the ionic charge of the waste counter ions. An appropriatesuspension of emulsified asphalt particles is then selected having anopposite particle charge to the ionic charge of the waste counter ions.The waste is then mixed with the selected suspension of emulsifiedasphalt particles at ambient temperature in an amount sufficient toreact with the waste counter ions and coalesce into a hydrophobic mass.It is disclosed that multivalent metal ions such as divalent calciumions are preferred for neutralizing anionic asphalt emulsion. Lime is apreferred source of such calcium ions. Sulphate ions such as found incalcium sulphate (gypsum) are a preferred neutralizing additive forcationic asphalt emulsion.

U.S. Pat. No. 4,615,809 discloses a method for stabilization of sludgesuch as organic sludge including combining the sludge with Portlandcement, fly ash, calcium sulfate dihydrate, and lime, optimally withstabilizing agents such as clay, recycled rubber, and ashphaltene, andan adsorbent for organic substances. The stabilized sludge compositionsprepared in accordance with this method are characterized by a soil-likeconsistency and low-volume expansion relative to sludge volumes prior tostabilization.

U.S. Pat. No. 4,465,518 discloses a process for strengthening soft soil.A high water content soft soil, for example from the sea or river bed,may be improved in strength by incorporating therein a finely divided,quenched iron blast furnace slag treated with sulfuric acid, and aPortland cement. The sulfuric acid-treated slag is a product obtained byreacting a finely divided, quenched iron blast furnace slag, such as awater-granulated iron blast furnace slag, with sulfuric acid to converta part of its calcium components into gypsum.

U.S. Pat. No. 4,457,781 discloses a method for solidifying waste slimesuspension. Solidification or colloidal argillaceous matter inessentially non-settling, aqueous slime media into a solid stable matrixis accomplished by mixing such slime with a hydratable calcium sulfateand hydrating to form an interlocking strength bearing matrix. Themethod is particularly useful for coalescing phosphatic clay slime withhydratable calcium sulfate prepared form the co-produced wastephosphogypsum.

U.S. Pat. No. 4,436,645 discloses a method for containing compositionsfor removal of pollutants from waste waters and methods of utilizingsame. Novel compositions containing fluoride are provided for theremoval of organic and heavy metal pollutants from waste waters andmethods of utilizing same. The compositions comprise components selectedfrom ion exchange absorbent gels, cements, water soluble fluoridecontaining salts and, optionally, alkali metal ortho-phosphates. Theprocedures of the present invention yield not only clarified waters butprovided a sludge which can be disposed of under environmentallyacceptable conditions.

On column 2, lines 61 et seq., it is stated that the cementitiouscomponent may be either a cement or a gypsum, however, this should besupplemented by a fourth component taken from either group (a) forexample, diatomaceous silica or from the cementitious group, (b) forexample, hydrated lime. In each it is preferred that the fourthcomponent be present in the same proportion (approximately) as the claycomponent.

U.S. Pat. No. 4,402,922 discloses a process for rapid conversion offluoroanhydrite to gypsum in which fluoroanhydrite is contacted with thefluid reaction medium slurry containing soluble sulfate ions and asubstantial proportion of small gypsum seed crystals to rapidly hydratea large proportion of the fluoroanhydrite to a coarser, substantiallypure gypsum. The slurry is clarified to separate coarse purified gypsumreaction product, and the reaction medium is reconstituted and recycledcontaining gypsum crystals less than the desired product size andconstituting about 50-90% of the reconstituted fluid reaction medium.The resultant gypsum is free of harmful soluble and semi-crystallizedimpurities and is acceptable for gypsum board manufacture.

U.S. Pat. No. 4,229,295 discloses a process for treating aqueous sludgecomprising a slurry of clay minerals and silica in water includingrapidly dispersing throughout the sludge at least one additive compoundselected from the group consisting of mineral acids, acid salts ofalkaline earth metals, alkaline earth metal oxides and alkaline earthmetal hydroxide. The additive is provided in an amount sufficient tocause formation in the sludge of large silicate molecules with resultantsolidification of the sludge by gelling and setting into an insert solidmaterial. The formation of calcium sulphate from the reactants isdisclosed.

U.S. Pat. No. 4,149,968 discloses a method of converting hazardousindustrial and other waste into an inert, non-polluting and usefulsolid-like product comprising mixing bentonite clays and Portlandcements with aqueous solutions or with mixtures containing pollutingmaterials to form a solid mass. The quantities of bentonite and cementcontrol the consolidation of materials and govern physical factors, suchas the hardness and the chemical characteristics of the resultantmaterial. The resulting product is chemically and physically stable; asolidified product which is completely insoluble in water, and in which,pollutants are encapsulated in the matrix so that the waste material isrender non-polluting and fit for ultimate disposal.

U.S. Patent 4,124,405 discloses a process for solidifying aqueous wasteand products thereof by treatment with a particulate metallurgical slagunder alkaline conditions in the presence of a hydration-promoting agentfor the slag, e.g., gypsum.

U.S. Pat. No. 4,028,130 discloses a disposal method and use of sewagesludge wherein digested sewage sludge resulting from sewage planttreatment of municipal sewage is disposed of and used in an ecologicallyacceptable manner by the incorporation of such sludge in hardenablecompositions further including, for example, lime, fly ash, and in somecases, alkaline earth metal sulfate and/or soil or other inert orcomplimentary additives. These hardenable compositions may be emplacedin an area open to the atmosphere and permitted to cure over a period oftime to act as land file or as road base materials. In column 2, lines35 through 38 states that preferably also these compositions include(based on weight percentage the solids) calcium sulfate (1.5-3% based onthe anhydrite) and 20-45% soil.

U.S. Pat. No. 3,947,284 discloses a method for solidifying sludge havinga water/solid high ratio and containing a substance having a harmfulinfluence upon the setting of Portland cement by mixing the sludge withhydraulic Portland cement and at least one substance selected from thegroup consisting of alkali sulphate, gypsum dihydrate and insolublegypsum anhydride.

U.S. Pat. No. 3,855,391 discloses a sludge stabilization with gypsumwherein a sulfur dioxide scrubber waste sludge is stabilized usingplaster of paris to product a stable landfill material. The scrubbingliquor is provided with a catalyst which optimizes the production ofcalcium sulfate as a solid sulfur compound in the scrubber waste. Thecalcium sulfate is separated from the waste sludge and converted byheating to plaster of paris, which is remixed with the sludge tostabilize the material as a landfill.

U.S Pat. No. 3,732,697 discloses a waste disposal method and facilitycomprises preparing a site with a relative flexible liner by spreadingsuccessive layers of the sandy soil amixed with potable water on the insitu native soil of the disposal site surface to provide a liner havinga thickness of several feet and mechanically compacting each of thesuccessive layers of sandy clay soil at approximately its optimumdensity to provide a water-impervious barrier which will protectunderground water supplies from chemical contamination by liquid wastematerials which are dumped on the top of the liner.

U.S. Pat. No. 3,720,609 discloses a process for treating aqueouschemical waste sludge and the composition produced thereby wherein wastesludge containing small amounts of certain types of reactive materialare treated by adding to such sludge materials capable of producingaluminum ions, lime and/or sulfate bearing compounds to produce acomposition having a sufficient concentration of sulfate ions, aluminumions and equivalents thereof, and calcium ions and equivalents thereof.Fly ash is the preferred source of aluminum ions for this purpose. Overa period of time such compositions harden by the formation of calciumsulfo-aluminate hydrates. Hardening of the sludge facilitates itsdisposition and may permit the reclamation of the land now occupied bylarge settling ponds for such sludge. Still further, the solidificationof such settling ponds may provide permanent land fill which permitsimmediate use of the land without the necessity for removal of thesludge. Aggregate materials may also be incorporated in the solidifiedwaste.

In column 3, lines 33 to 38, it is stated that materials of varioustypes may be added to raised the available sulfate ions concentration asneeded. Typical of these are calcium sulfate anhydrite, calcium sulfatehemihydrate (plaster of paris) and calcium sulfate dihydrate (gypsum).

U.S. Pat. No. 1,471,201 discloses a method of producing a material forthe treatment of oils including producing a decolorizing and purifyingagent for oils, which consists in first forming a mudded mass fromnon-spent mineral earth, then subjecting the mudded mass to the actionof an acid for the separation therefrom of acid soluble bodies, removingthe acid and reaction products from the insoluble portion of the mass bythe application of water, thickening the mass by the withdrawal ofexcess water therefrom, and maintaining the treated body until used in amudded condition to prevent contact of air with the solid particlesthereof.

SUMMARY OF THE INVENTION

In accordance with present invention there is provided a solidificationmaterial, and a process for the production of the solidificationmaterial, for use in solidifying liquid waste and sludge. The wastesolidification material is prepared from fluorogypsum which is aby-product of the industrial production of hydrogen fluoride. In theindustrial production of hydrogen fluoride, fluorspar is reacted withconcentrated sulfuric acid in heated reaction vessel to co-producehydrogen fluoride and calcium sulfate. Hydrogen fluoride is removed andthe calcium sulfate and impurities are slurried with water which isreferred to herein as fluorogypsum.

The process of the present invention includes drying the fluorogypsum toevaporate water physically bound with the fluorogypsum, further dryingthe fluorogypsum to reduce the chemically bound water to from about 0.5%to about 9% by weight of calcium sulfate, and crushing the resultantmaterial to a desired particle size range. The product produced by theprocess of the invention may then be mixed with chemical waste sludgeand/or liquid to solidify the chemical waste sludge and/or liquid.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The material of the invention is made from a by-product produced by thereaction of fluorspar with sulfuric acid in the industrial production ofhydrofluoric acid. The hydrogen fluoride is removed after the reaction,while the by-product, which is predominantly calcium sulfate, isslurried with water and pumped into disposal ponds. Excess watereventually evaporates and/or hydrates with calcium sulfate in the slurryand the by-product hardens. The dry by-product contains about 99% byweight calcium sulfate anhydrite and calcium sulfate having waterchemically combined therewith, plus small quantities of fluorinecontaining compounds small concentrations of sulfuric acid, or othertrace elements and compounds. The by-product is sometimes referred toherein as fluorogypsum. The pH of the fluorogypsum is typically fromabout 3 to about 5 at some hydrofluoric acid plants, and from about 3 toabout 13 at other hydrofluoric plants.

In accordance with the invention, fluorogypsum is first heated toevaporate water physically mixed with the fluorogypsum. Secondly,heating is continued to partially remove water chemically bound withcalcium sulfate. If all water chemically bound with calcium sulfate isremoved, the end product does not efficiently solidify wastes. It isimportant that only from about 0.5% to about 9% by weight of waterremains chemically bound to calcium sulfate for the resultant product toefficiently solidify wastes; more preferably, from about 1.0% to about9.0% by weight of water remains chemically bound to calcium sulfate;most preferably, from about 1.5% to about 6.0% by weight of waterremains chemically bound to calcium sulfate.

After the chemically bound water is reduced to the desired range, thesolidification material of the invention is crushed or sized to aparticle size of from bout 5000 microns to about 37 microns, morepreferably from about 1000 microns to about 37 microns, most preferablyfrom about 150 microns to about 37 microns.

In following examples 1-25, the physically mixed water was first removedby heating the fluorogypsum in an oven at a temperature of about 90° F.Once the physically mixed water was removed, the temperature in the ovenwas raised to above 105° F. which is the temperature above which thechemically bound water will be released.

In the following examples 1-25, "Set" was determined by mixing about 50grams of the dried fluorogypsum with about 40 grams of water, and themixture was allowed to stand at room temperature of about 72° F. Themixture is observed after about one hour to determine if the mixturehardens. If the mixture hardens sufficiently to support a load of about50 pounds per square inch, the notation "good" is made in the columnlabeled "Set". If the mixture is soft, the notation "poor" is made inthe column labeled "Set".

The percentage weight loss is the percentage decrease in weight of thesample which occurs after heating due to the chemically bound waterbeing released.

The percentage chemical water loss is the weight percent of chemicallybound water remaining in the waste solidification material afterheating.

    __________________________________________________________________________    HEATING TIME FOR REMOVING CHEMICALLY BOUND WATER                              IN DRY FLUOROGYPSUM                                                                  HEATING      SAMPLE       % CHEM.                                      EXAMPLE                                                                              TIME         WEIGHT                                                                              % WEIGHT                                                                             WATER                                        NO.    MINUTES                                                                             TEMP.  (GRAMS)                                                                             LOSS   LOSS  SET                                    __________________________________________________________________________    1      5 min.                                                                              1000°                                                                       F.                                                                              50.0  10.6   0     Poor                                   2      10 min.                                                                             1000°                                                                       F.                                                                              50.0  20.4   2.3   Good                                   3      5 min.                                                                              1100°                                                                       F.                                                                              50.0  9.6    9.6   Poor                                   4      10 min.                                                                             1100°                                                                       F.                                                                              50.0  15.8   2.8   Good                                   5      15 min.                                                                             1100°                                                                       F.                                                                              5.0   16.8   3.7   Good                                   6      30 min.                                                                             284°                                                                        F.                                                                              100   8.7    2.7   Good                                   7      5 min.                                                                              1000°                                                                       F.                                                                              50.0  10.0   0     Poor                                   8      10 min.                                                                             1000°                                                                       F.                                                                              50.0  21.4   5.6   Good                                   9      10 min.                                                                             1000°                                                                       F.                                                                              50.0  26.7   6.9   Good                                   10     8 min.                                                                              850-900°                                                                    F.                                                                              50.0  13.8   100   Poor                                   11     10 min.                                                                             850-900°                                                                    F.                                                                              50.0  18.0   1.4   Good                                   12     15 min.                                                                             859-900°                                                                    F.                                                                              50.0  25.0   6.7   Good                                   13     5 min.                                                                              700°                                                                        F.                                                                              50.0  8.8    0     Poor                                   14     10 min.                                                                             700°                                                                        F.                                                                              50.0  15.0   100   Poor                                   15     13 min.                                                                             850°                                                                        F.                                                                              50.0  16.0   3.7   Good                                   16     15 min.                                                                             850°                                                                        F.                                                                              50.0  9.6    2.1   Good                                   17     5 min.                                                                              850°                                                                        F.                                                                              50.0  8.0    0     Poor                                   18     5 min.                                                                              1100°                                                                       F.                                                                              50.0  15.0   3.5   Good                                   19     10 min.                                                                             1100°                                                                       F.                                                                              50.0  17.0   3.9   Good                                   20     1 min.                                                                              1300°                                                                       F.                                                                              50.0  3.0    0     Poor                                   21     3 min.                                                                              1300°                                                                       F.                                                                              50.0  9.0    1.2   Good                                   22     5 min.                                                                              1300°                                                                       F.                                                                              50.0  14.0   3.5   Good                                   23     1 min.                                                                              1400°                                                                       F.                                                                              50.0  5.0    1.6   Good                                   24     5 min.                                                                              1400°                                                                       F.                                                                              50.0  17.0   3.9   Good                                   25     1 min.                                                                              1800°                                                                       F.                                                                              50.0  17.0   3.9   Good                                   __________________________________________________________________________

EXAMPLE 26

Fluorogypsum produced as a by-product of making hydrofluoric acid byreacting fluorspar with sulfuric acid was placed in the entrance of a 48foot long rotating furnace heated at its entrance to about 1000° F. Thefluorogypsum traversed 48 feet through the furnace in about 15 minutes.Exit temperature of the furnace was 200° to 300° F.

    __________________________________________________________________________    HEATING TIME FOR REMOVING CHEMICALLY BOUND WATER                              IN DRY FLUOROGYPSUM                                                                  HEATING    SAMPLE       % CHEM.                                        EXAMPLE                                                                              TIME       WEIGHT                                                                              % WEIGHT                                                                             WATER                                          NO.    MINUTES                                                                             TEMP.                                                                              (GRAMS)                                                                             LOSS   LOSS  pH SET                                   __________________________________________________________________________    27.    5     1000° F.                                                                    50.0  6.4    0     8.5                                                                              Poor                                  28.    10    1000° F.                                                                    50.0  10.4   4.0   8.5                                                                              Good                                  29.    5     1100° F.                                                                    50.0  8.7    0     12.5                                                                             Poor                                  30.    10    1100° F.                                                                    50.0  12.6   3.5   12.5                                                                             Good                                  31.    15     900° F.                                                                    50.0  9.1    6.1   4.8                                                                              Good                                  32.    10    1100° F.                                                                    50.0  8.8    5.8   4.6                                                                              Good                                  33.    5      850° F.                                                                    50.0  7.1    0     5.2                                                                              Poor                                  34.    8      850° F.                                                                    50.0  9.7    0     5.3                                                                              Poor                                  35.    12     850° F.                                                                    50.0  12.1   2.1   5.4                                                                              Good                                  36.    15    1200° F.                                                                    50.0  16.0   16.0  7.9                                                                              Poor                                  37.    10    1000° F.                                                                    50.0  8.1    0     3.4                                                                              Poor                                  38.    15    1000° F.                                                                    50.0  9.9    1.0   3.4                                                                              Good                                  39.    10     950° F.                                                                    50.0  7.0    1.5   4.1                                                                              Good                                  40.    15     950° F.                                                                    50.0  9.1    2.9   4.2                                                                              Good                                  41.    20     750° F.                                                                    50.0  10.8   3.9   4.4                                                                              Good                                  42.    15     875° F.                                                                    50.0  10.2   3.3   4.3                                                                              Good                                  43.    20     875° F.                                                                    50.0  11.7   4.6   4.5                                                                              Good                                  44.    10    1100° F.                                                                    50.0  12.0   0     3.5                                                                              Poor                                  45.    10    1000° F.                                                                    50.0  14.0   0     3.8                                                                              Poor                                  46.    10    1300° F.                                                                    50.0  17.0   3.7   3.8                                                                              Good                                  __________________________________________________________________________

The waste solidification material was dry, i.e., it continuedsubstantially no physically mixed water. Chemically bound water wasabout 7% by weight.

Particle size of the sample ranged from about 37 microns to about 250microns. Density was 62 pounds per cubic feet

Fifty grams of the waste solidification material was mixed with about 35grams of water, and the mixture became solid within five minutes at anambient temperature of about 72° F. and ambient pressure of approximatedsea level.

When substantially all (at least 99.5%) the physically mixed water isremoved from fluorogypsum, there still remains 11-12% by weight waterchemically bound to calcium sulfate. The fluorogypsum will bind orabsorb only about 20-30% by weight water when the 11-12% chemicallybound water is present in the fluorogypsum.

When the water chemically bound to the calcium sulfate is reduced toabout 0.5 to about 9% by weight, the waste solidification material ofthe invention will absorb or bind water in the amount of about 90% to100% of the weight of the waste solidification material.

Normally, since fluorogypsum storage piles are uncovered and exposed tothe atmosphere, the amount of physically mixed water in fluorogypsumfluctuates depending upon the climate. For example, more water isphysically mixed with fluorogypsum during the wet winter months than inthe drier, hotter months. However, no matter how much physically mixedwater is present, physically water should be removed before thechemically bound water can be released.

Although the preferred embodiments of the present invention have beendisclosed and described in detail above, it should be understood thatthe invention is in no sense limited thereby, and its scope is to bedetermined by that of the following claims:

What is claimed is:
 1. A process for the preparation of a wastesolidification material from hardened fluorogypsum having a pH ofgreater than about 5 to about 13 produced as a by-product of themanufacture of hydrofluric acid by reacting fluorspar with sulfuricacid, removing hydrogen fluoride from the reaction product, slurryingthe by-product in settlement ponds until the by-product fluorogypsumhardens, comprising:a. heating said hardened fluorogypsum having a pH ofgreater than about 5 to about 13 for a time sufficient to evaporatesubstantially all water physically mixed with said hardenedfluorogypsum, and b. further heating said hardened fluorogypsum at atemperature above 105° F. for a time sufficient to reduce waterchemically bound to calcium sulfate in said hardened fluorogypsum tofrom about 0.5% to about 9% by weight.
 2. The process of claim 1 whereinsaid waste solidification material is crushed to a particle size rangeof from about 5000 microns to about 37 microns.
 3. The process of claim2 wherein said waste solidification material has a particle size rangeof from about 1000 microns to about, 37 microns.
 4. The process of claim1 wherein said water chemically bound to said calcium sulfate in saidfluorogypsum is reduced to from about 1.0% to bout 9.0% by weight. 5.The process of claim 4 wherein said waste solidification material has aparticle size range of from about 1000 microns to about 37 microns. 6.The process of claim 4 wherein said waste solidification material has aparticle size range pf from about 150 microns to about 37 microns. 7.The process of claim 6 wherein said water chemically bound to saidcalcium sulfate in said fluorogypsum is reduced to from about 11/2% toabout 6.0% by weight.
 8. The process of claim 1 wherein said waterchemically bound to said calcium sulfate in said fluorogypsum is reducedto from about 11/2% to about 6.0% by weight.
 9. The process of claim 1wherein said waste solidification material has a particle size rangefrom about 150 microns to about 37 microns.
 10. A material suitable foruse as a waste solidification material comprising:a. substantially dry,hardened, particulate fluorogypsum containing, in combination, about 99%by weight calcium sulfate anhydrite and calcium sulfate having waterchemically bound to said calcium sulfate, said water chemically bound tosaid calcium sulfate being present in an amount of from about 11/2% toabout 9% by weight. b. said waste solidification material having aparticle size range of from about 5000 microns to about 37 microns, andc. said material having a pH of from greater than about 5 to about 13.11. The product of claim 10 wherein said water chemically bound to saidcalcium sulfate is from about 1% to about 9% by weight.
 12. The productof claim 10 wherein said water chemically bound to said calcium sulfateis reduced from about 11/2% to about 6% by weight.
 13. The product ofclaim 10 wherein said waste solidification material has a particle sizerange of from about 1000 microns to about 37 microns.
 14. The product ofclaim 10 wherein said waste solidification material has a particle sizerange of from about 150 microns to about 37 microns.
 15. A process forthe preparation of a waste solidification material from hardenedfluorogypsum having a pH of from greater than about 3 to about 13produced as a by-product of the manufacture of hydrofluoric acid byreacting fluorspar with sulfuric acid, removing hydrogen fluoride fromthe reaction product, slurrying the by-product in settlement pond untilthe by-product fluorogypsum hardens, said hardened fluorogypsum having apH of from greater than about 3 to about 13, comprising heating saidfluorogypsum in a rotating furnace at a temperature above 105° F. for atime sufficient to reduce water chemically bound to calcium sulfate insaid hardened fluorogypsum to from about 0.5% to about 9% by weight. 16.The process of claim 15 wherein said waste solidification material has aparticle size range of from about 1000 microns to about 37 microns. 17.The process of claim 16 wherein said waste solidification material has aparticle size range of from about 150 microns to about 37 microns. 18.The product of claim 17 wherein said water chemically bound to saidcalcium sulfate is from about 11/2% to about 6.0% by weight.
 19. Theproduct of claim 16 wherein said water chemically bound to said calciumsulfate is from about 1.0% to about 9.0% by weight.